Fluid dispensing in a range of picoliters (pL) to microliters (μL) is often used in biological and pharmaceutical research and development, medical diagnosis and examination, or agricultural testing. For example, in studying a dose-response effect of chemotherapy, fluid dispensing with a low volume is an important task for determining the concentration of a candidate compound required to effectively attack cancer cells.
In such dose-response experiments, candidate compounds are prepared at many different concentrations in the micro-sized wells of a multi-well plate to determine an effective concentration. An existing on-demand type droplet ejecting head is used for the above application. For example, the droplet ejecting head includes a storage container that holds a solution, a nozzle that ejects the solution, a pressure chamber that is disposed between the container and the nozzle, and an actuator that controls pressure of the solution inside the pressure chamber to eject the solution from the nozzle.
In the droplet ejecting head, the volume of one droplet ejected from an individual nozzle is on the order of a picoliter (pL). By controlling the total number of droplets ejected into each well, the droplet ejecting head supplies an amount of fluid in a range of picoliter to microliters into each well. Therefore, the droplet ejecting head is generally suitable for dose-response experiments when dispensing the candidate compounds at various concentrations or when dispensing in very small amounts.
The actuator in the droplet ejecting head can be a piezoelectric actuator that has a structure having a nozzle that ejects droplets.